I've been flying my friends RV-8. He's got a becker transponder in it with mode S and ADSB out. The tower told us he did not see the transponder. Then we go and look on Flight Aware and there it is. Showing the entire flight. How can the tower not see our transponder, yet we show up on flight aware? What's going on? He thinks it's mode S working, but the mode A & C are not. our tower only looks for mode A? I'm skeptical. Any ideas?